1. Field of the Invention
This invention generally relates to a process for manufacturing a semiconductor device, and, in particular, to a wafer process in the manufacture of a semiconductor device using a phosphosilicate glass as an interlayer insulating or passivation film. More specifically, the present invention relates to a technique of etching a phosphosilicate glass film selectively ion-implanted with boron.
2. Description of the Prior Art
A wafer process in the manufacture of a semiconductor device having a phosposilicate glass (also referred to as PSG, hereinafter) film includes a step for forming a contact hole, via or a bonding pad, and a step for smoothing the surface by removing sharp steps. It is known that the etch rate of a phosphosilicate glass film against hydrofluoric acid (HF) is high but a boron phosphosilicate glass (also referred to as BPSG, hereinafter) film, which has been formed by the CVD method with boron contained in phosphosilicate glass, has a lower etch rate against HF as compared with the ordinary PSG film. However, in such a BPSG film formed by the CVD method, boron atoms are contained in the resulting film uniformly.
Heretofore, no proposal has been made to utilize the fact of difference in etch rate depending on the amount of contents of boron atoms in a PSG film for processing the PSG film to form contact holes or the like.